The early stages of the formation of persistent slip markings in fatigue were analyzed using three-dimensional discrete dislocation dynamics modelling. Surface displacements due to slip were computed using a specific post-processing method. Fatigue simulations under various strain ranges and grain sizes were performed. The resulting surface slip markings and their evolutions were analyzed quantitatively in terms of marking height and thickness. A detailed scheme for persistent slip marking formation and morphology was proposed in relation to the persistent slip-band dislocation arrangements present within the grain. The simulations showed the crucial role of these arrangements for the extrusion-intrusion growth and localization of slip at the band edges. Local stress concentrations inside the crystal and their relationship to damage initiation were also analyzed. The results provided insights for an original micro-crack initiation scheme, combining different initiation mechanisms as described in the literature.

Low-Strain Fatigue in 316L Steel Surface Grains - a Three Dimension Discrete Dislocation Dynamics Modelling of the Early Cycles - Part 2 - Persistent Slip Markings and Micro-Crack Nucleation. C.Déprés, C.F.Robertson, M.C.Fivel: Philosophical Magazine, 2006, 86[1], 79-97